Dental infection as a cause of bacteraemia in infective endocarditis

Infective endocarditis is an infection of the inner surface of the heart, the endocardium, and can include the heart valves, mural endocardium or a septal defect. There are three factors that contribute to the development of infective endocarditis; the introduction of bacteria into the bloodstream, a predisposing valve defect, and the virulence of the bacteria. Due to a pre-existing valve defect, such as congenital defects, rheumatic fever or prosthetic heart valves, a sterile thrombus forms and it is this thrombus that bacteria adhere to and invade and eventually form vegetations. Increased numbers of bacteria from the bloodstream accumulate, the vegetation grows and prevents normal valvular function. Eventually this can lead to congestive heart failure. Sometimes, parts of these vegetations can break off and enter the bloodstream where they can cause cerebral infarction, aneurysms and can cause infections in distant organs.¹

Oral bacteria can be introduced into the bloodstream from carious or infected teeth. Staphylococcus aureus and Streptococcus viridans can be present in the oral cavity and are the most common organisms responsible for infective endocarditis. Streptococcus viridans are highly cariogenic and have been isolated from blood cultures and from vegetations on heart valves in a significant proportion of infective endocarditis cases.²